Dumbfound

Lashes a target you can see within range with a psychic whip that seeks to debilitate its mind. The target takes 2d6 hitpoints of psychic damage and on a failed save, its intelligence, wisdom or charisma (the caster chooses which, which also determines the appropriate saving throw needed) score drops by 1d4 + 1. If a target’s intelligence, wisdom or charisma drops to 0, it dies.

If the target is a spellcaster and their spellcasting ability score drops to 9 or less, they are considered to be ‘dumbfounded’. Dumbfounded spellcasters can no longer cast spells until their spellcasting ability score returns to 10 and above. Multiple castings can be devastating. This can only be reversed by the spells Heal, Greater restoration or Wish. Otherwise, the target's affected ability score steadily returns to normal at the rate of 1 point recovered per day. A successful saving throw negates the ability score reduction but not the damage.